Swedish Covid-19 Investigation for Future Insights – A Population Epidemiology Approach Using Register Linkage (SCIFI-PEARL)

Abstract

Background In response to the Covid-19 pandemic, we designed and initiated a nationwide linked multi-register, regularly updated, observational study for timely response to urgent scientific questions. Aim To describe the SCIFI-PEARL (Swedish Covid-19 Investigation for Future Insights – a Population Epidemiology Approach using Register Linkage) linked database encompassing essentially all known diagnosed Swedish Covid-19 patients plus a large general population comparison cohort and outline its utility in the current and future phases of the pandemic. Methods Individuals with Covid-19 from the entire country are identified on a regularly updated basis, from different sources: all individuals from SmiNet, the national database of notifiable diseases, with positive SARS-CoV-2 polymerase chain reaction (PCR) test results; patients identified in the healthcare system by condition (ICD-10) or procedure codes in the National Patient Register or Cause-of-Death Register; patients identified through several disease-specific national quality registers (NQRs); and in two regions additionally patients identified in primary care. A comparison population was obtained by stratified random sampling from Swedish national population registers. Data from all these registers plus the National Prescribed Drug Register, the Cancer Register, national sociodemographic registers, some additional NQRs, the National Vaccination Register, and further data sources, are then linked to all study subjects (Covid-19 cases and population cohort). New cases in the study population and all data for all subjects are updated every few months, as required. Conclusion and Utility The SCIFI-PEARL study cohort captures Swedish residents with Covid-19 on an ongoing basis, includes a representative general population comparison cohort, and links to a broad range of national and regional healthcare data for a comprehensive longitudinal view of the Covid-19 pandemic. By combining high-quality national registers with short time delay and continuous repeated linkage and updating, the project brings timely and internationally relevant data for epidemiological research on SARS-CoV-2. Our efforts provide an example and important learnings for similar efforts internationally in the future.

The social patterning of Covid-19 vaccine uptake in older adults: A register-based cross-sectional study in Sweden

“…The SCIFI-PEARL project is based on a linked and regularly updated database including all registered individuals in Sweden diagnosed with Covid-19, together with a large general population cohort, described in detail elsewhere. 23 The database constitutes a nationwide observational study based on multiple health and population registers linked with high accuracy (close to 100%) and quality using the unique Swedish Personal Identity Number (PIN). 24 The general population comparison cohort was obtained from the National Register of the Total Population (RTB) at Statistics Sweden and comprised about ten percent of all individuals of all ages living in Sweden on 1 January 2020.…”

“… 19 However, recent research has indicated that taking several overlapping social dimensions into account at the same time can contribute to a more nuanced understanding of socioeconomic disparities in health. 20 , 21 , 22 In the present study, based on data from the nationwide linked multi-register observational study SCIFI-PEARL (Swedish Covid-19 Investigation for Future Insights – A Population Epidemiology Approach Using Register Linkage), 23 we examined sociodemographic determinants associated with Covid-19 vaccination uptake in the general Swedish population aged 60 years or older during the first five months of the Covid-19 vaccination program. Also, heterogeneity within sociodemographic groups was studied by using intersectional analysis models that have previously been suggested for detailed sociodemographic characterisation.…”

Occupation and COVID-19 diagnosis, hospitalisation and ICU admission among foreign-born and Swedish-born employees: a register-based study

“…This study is part of the SCIFI-PEARL (Swedish COVID-19 Investigation for Future Insights-a Population Epidemiology Approach using Register Linkage) project, a nationwide multiregister-based observational study designed in response to the COVID-19 pandemic. Details about the project have been published elsewhere 22. Briefly, the project includes regularly updated data of all individuals with COVID-19 identified from different registers in Sweden.…”

Adverse events of special interest for COVID-19 vaccines - background incidences vary by sex, age and time period and are affected by the pandemic

“…The analyses were based on the larger SCIFI-PEARL (Swedish Covid-19 Investigation for Future Insights -a Population Epidemiology Approach using Register Linkage) project, which has been described elsewhere (9). A subproject known as RECOVAC (Register-based large-scale national population study to monitor Covid-19 vaccination effectiveness and safety) focuses on COVID-19 vaccination research questions and this analysis is a first component of that effort.…”

“…The study population was identified from national registers at Statistics Sweden, with age and sex data. To this study population we linked data from the National Patient Register (NPR), which includes data on all hospitalizations and outpatient specialist care visits in Sweden, including date of admission or date of visit and diagnoses coded with International Classification of Diseases version 10 (ICD-10) codes, Swedish national version (9).…”